Integrated piezoelectric sensing ceramic core shell and method of making and monitoring

Abstract

The application provides an integrated ceramic core shell integrated with a piezoelectric sensor, and a preparation and monitoring method thereof, and relates to the technical field of ceramic core preparation.The ceramic core shell comprises a ceramic base formed through an additive manufacturing process, a piezoelectric sensing unit embedded in a monitoring area, a protective shell for sealing the sensing unit, and a signal transmission line embedded in the protective shell.The preparation method comprises the following steps: determining the monitoring area based on thermal-mechanical coupling simulation and constructing a three-dimensional digital model; printing the ceramic base, the piezoelectric sensing unit and its polarization electrode, and the synchronously formed protective shell and signal transmission line in sequence through a multi-material additive manufacturing process; and performing integrated sintering and polarization treatment on the green body.The application realizes integrated manufacturing and integration of the sensor and the ceramic structure, and solves the problem that traditional external sensors cannot reliably monitor the inside of a high-temperature and complex-structure casting core.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic core preparation, in particular to an integrated ceramic core shell integrated with a piezoelectric sensor and a preparation and monitoring method thereof. BACKGROUND

[0002] In the fields of aerospace, energy power and high-end equipment manufacturing, the performance of high-temperature alloy complex structure castings directly determines the effectiveness and reliability of core equipment. The production of such castings generally adopts investment precision casting process, the core of which is to use ceramic cores and shells with specific high-temperature mechanical properties and thermal chemical stability to form the complex inner cavity and shape of the castings.

[0003] During the casting process, ceramic cores and shells need to withstand the thermal impact of molten metal far exceeding their conventional service temperature, and be in a high-temperature thermal gradient environment for a long time. Under such extreme conditions, ceramic materials are extremely susceptible to unpredictable and non-uniform thermal deformation due to the coupling effects of multiple physical and chemical effects such as thermal expansion coefficient mismatch, sintering shrinkage, phase transition and gravity creep. This phenomenon has become a key bottleneck restricting the yield and performance improvement of high-end castings. Specifically, the thermal deformation of the core / shell will be directly transmitted to the solidifying castings, causing uncontrollable deviations in their critical dimensions, and in severe cases, internal defects such as shrinkage and hot cracking, resulting in substandard mechanical properties of the castings, and ultimately causing high waste costs and resource waste.

[0004] To quantify and control this process, it is crucial to accurately monitor the thermal deformation behavior of ceramic cores / shells at high temperatures. However, the existing mainstream monitoring technologies have fundamental limitations. One is the strain gauge measurement method: this method has a sharp performance degradation in high-temperature environments, and the complex pasting process and lead difficulty make it difficult to achieve reliable and consistent measurement on complex surfaces. Another is the contact displacement sensor method: its response speed is slow, and it cannot capture the dynamic deformation process, and the existence of physical probes severely limits the installation location, making it difficult to achieve global monitoring.

[0005] The existing patent CN120533058A discloses an alloy die casting temperature field control method and system for reducing thermal cracks, the core of which is to optimize the solidification process of the castings by externally regulating the mold temperature field, its focus is on the prevention and control of thermal cracks of the alloy itself, which belongs to the control and optimization of process parameters, and does not involve direct measurement of the deformation of the ceramic core / shell body at high temperatures.

[0006] The existing patent CN114923917A discloses a ceramic core correction and detection integrated method, the core of which is the correction and geometric size detection of the ceramic core at room temperature or lower temperature after sintering is completed, and the technical focus is on the "after-the-fact" correction and profile measurement of the finished product, which cannot be applied to the high-temperature environment of casting to realize real-time perception of the dynamic process of thermal deformation of the core / shell.

[0007] In summary, the above existing patents do not solve the fundamental problem of in-situ, real-time and accurate thermal deformation monitoring of the ceramic core / shell in the high-temperature environment of casting. SUMMARY

[0008] Based on the above problems existing in the prior art, the present application proposes an integrated ceramic core shell integrated with piezoelectric sensing and its preparation and monitoring method. By synchronously forming the piezoelectric sensing unit and the ceramic core shell using an integrated additive manufacturing process, an internal monitoring system with structural symbiosis is formed, thereby solving the problem that traditional external sensors cannot realize in-situ, real-time and accurate monitoring of complex structure ceramic core shell in high-temperature environment.

[0009] To achieve the above-mentioned purpose, the first aspect of the present application proposes an integrated ceramic core shell integrated with piezoelectric sensing, and the specific technical solutions are as follows:

[0010] An integrated ceramic core shell integrated with piezoelectric sensing, comprising:

[0011] A ceramic matrix formed by an additive manufacturing process;

[0012] At least one piezoelectric sensing unit built in a monitoring area of the ceramic matrix by an additive manufacturing process, the piezoelectric sensing unit comprising a piezoelectric ceramic layer and a polarization electrode layer formed on the surface thereof;

[0013] A protective shell formed by an additive manufacturing process and sealingly covering the piezoelectric sensing unit;

[0014] A signal transmission line formed by an additive manufacturing process synchronously with the protective shell and embedded in the protective shell, one end of the signal transmission line being connected to the polarization electrode layer and the other end extending to the outer surface of the ceramic core shell.

[0015] Further, the monitoring area is determined based on thermal-mechanical coupling simulation analysis of the ceramic core shell during thermal processing, and the monitoring area is the area where the equivalent stress value exceeds the preset stress threshold or the total deformation exceeds the preset deformation threshold in the simulation results.

[0016] Further, a fitting gap for compensating for sintering shrinkage is formed between the protective shell and the ceramic matrix, and the value range of the fitting gap is 30-70μm.

[0017] To achieve the above object, the second aspect of the present application proposes a preparation method of integrated piezoelectric sensing integrated ceramic core shell, and the specific technical solutions are as follows:

[0018] A preparation method of integrated piezoelectric sensing integrated ceramic core shell is used to prepare the integrated piezoelectric sensing integrated ceramic core shell mentioned above, and includes the following steps:

[0019] S1, determining the monitoring area of the ceramic matrix based on thermal-mechanical coupling simulation analysis, and constructing a three-dimensional digital model of the ceramic core shell;

[0020] S2, based on the three-dimensional digital model, printing the ceramic matrix using an additive manufacturing process;

[0021] S3, using an additive manufacturing process, printing the piezoelectric sensing unit and its polarization electrode in the monitoring area of the ceramic matrix;

[0022] S4, printing a protective shell covering the piezoelectric sensing unit through a multi-material additive manufacturing process, and synchronously printing a signal transmission line;

[0023] S5, sintering the printed green body;

[0024] S6, polarizing the piezoelectric sensing unit through the signal transmission line.

[0025] Further, in step S1, the construction of the three-dimensional digital model of the ceramic core shell includes the construction of the three-dimensional digital model of the ceramic matrix fused with the piezoelectric sensing unit, the protective shell and the signal transmission line; wherein a mounting groove is generated in the monitoring area of the ceramic matrix, the inner cavity shape of the mounting groove is complementary to the outer shape of the protective shell; and the layout path of the signal transmission line is planned.

[0026] Further, in step S2, light-cured 3D printing is used to print the ceramic matrix with mounting groove by controlling the printing layer thickness and exposure energy; wherein the solid content of the silica-based ceramic slurry used is 75-86wt%, and the particle size of the ceramic powder is 1-20µm; the layer thickness of the light-cured 3D printing is 40-80µm, and the single-layer exposure energy is 40-70mW.

[0027] Further, in step S3, the piezoelectric sensing unit is printed by micro-droplet jetting technology, and the piezoelectric ceramic slurry with a solid content of 75-86wt% is filled into the mounting groove, and the temperature of the printing process is 80℃-120℃.

[0028] Further, in step S5, the sintering process includes: heating to 500-650 DEG C and holding to complete debinding in air atmosphere, and then heating to 1100-1350 DEG C and sintering holding in argon protective atmosphere.

[0029] Further, in step S6, the polarization process includes: applying 1-5 kV / mm of direct current electric field in the polarization liquid environment at a temperature of 150-220 DEG C for 10-50 min.

[0030] To achieve the above object, the third aspect of the present application proposes a monitoring method of integrated piezoelectric sensing integrated ceramic core shell, and the specific technical scheme is as follows:

[0031] A monitoring method of integrated piezoelectric sensing integrated ceramic core shell is used to monitor the integrated piezoelectric sensing integrated ceramic core shell, and includes the following steps:

[0032] Through experimental calibration, a corresponding relationship model between the resonance frequency offset of the piezoelectric sensing unit and the thermal deformation of the ceramic core shell is established;

[0033] In the thermal processing process, the resonance frequency data of the piezoelectric sensing unit are collected in real time;

[0034] Based on the established corresponding relationship model, the collected resonance frequency data are converted into thermal deformation and the monitoring result is output, and when the thermal deformation exceeds a preset threshold, a warning is triggered.

[0035] The above technical scheme of the present application at least realizes the following technical effects:

[0036] 1. The present application synchronously prints the piezoelectric sensing unit in the internal of the ceramic core shell in the manufacturing process of the ceramic core shell through the integrated additive manufacturing process, and forms a micro-level fusion interface. This fundamentally eliminates the problems of falling and signal drift caused by high-temperature failure of adhesive or thermal expansion mismatch of the traditional "after-mounted" sensor, and lays a solid foundation for realizing long-term, stable and reliable monitoring in an extreme high-temperature environment above 600 DEG C.

[0037] 2. The present application precisely shapes the piezoelectric sensing unit in the key positions such as complex internal cavities which cannot be reached by traditional means, realizes global and in-situ monitoring of the stress and deformation state of the complex structure, and solves the long-existing problem of monitoring blind area.

[0038] 3. The present application determines the key monitoring area through thermal-mechanical coupling simulation, realizes the collaborative optimization of structure design and sensor layout, controls the printing parameters, not only ensures the macro-size precision, but also directly shapes the microstructure and performance of the piezoelectric sensing unit, so as to ensure that each product has highly consistent sensing precision and response speed.

[0039] 4. The present application combines the complex "structure manufacturing" and "function integration" multiple processes into "one-time forming", greatly simplifying the process and shortening the cycle. At the same time, the real-time accurate monitoring data provided can be directly used to guide the process parameter optimization, forming a closed-loop control, thereby significantly improving the size qualified rate of high-end castings, reducing the scrap rate, and realizing cost reduction and efficiency increase.

[0040] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0041] The drawings constituting a part of the specification of the present application are used to propose a further understanding of the present application, the illustrative embodiments of the present application and the description thereof are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0042] Figure 1 A flowchart of a preparation method of an integrated piezoelectric sensing integrated ceramic core shell is shown;

[0043] Figure 2 A flowchart of a monitoring method of the integrated piezoelectric sensing integrated ceramic core shell is shown. DETAILED DESCRIPTION

[0044] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0045] The present application will be further described in detail below in combination with specific embodiments, which cannot be understood as limiting the scope of the present application.

[0046] According to a first aspect of the present application, an integrated piezoelectric sensing integrated ceramic core shell for preparing a turbine blade of an aero-engine is provided. The integrated ceramic core shell includes a ceramic base, a piezoelectric sensing unit, a protective shell, and a signal transmission line. The piezoelectric sensing unit is embedded and fixed in the mounting groove of the ceramic base through an additive manufacturing process, the protective shell is completely covered and sealed by the piezoelectric sensing unit through an additive manufacturing process, and the signal transmission line is synchronously formed with the protective shell through an additive manufacturing process and is embedded in the ceramic base and the protective shell. One end of the signal transmission line is connected to the electrode of the piezoelectric sensing unit, and the other end forms a connection end exposed to the outer surface of the ceramic core shell.

[0047] Specifically, the material of the ceramic base and the protective shell is silica-based ceramic, the thermal deformation monitoring area of the ceramic base is an area where the equivalent stress value exceeds the stress threshold value or an area where the total deformation exceeds the size threshold value. The mounting groove is arranged in the monitoring area to ensure that the piezoelectric sensing unit can effectively capture the most representative thermal deformation information. The shape of the protective shell and the inner cavity of the mounting groove are designed as complementary structures that match each other. The mounting groove is a negative cavity formed by the ceramic base material, and the protective shell is a positive entity that fills the cavity. They form a geometric conformal relationship in three-dimensional space. This design ensures that the protective shell can be accurately positioned and constrained in the mounting groove. At the same time, a matching gap is provided between the protective shell and the ceramic base to compensate for the size change of the material during subsequent sintering. Finally, the sintering combination is dense and firm at the interface by co-sintering. The protective shell can protect the piezoelectric sensing unit from high-temperature metal liquid impact and chemical corrosion.

[0048] Optionally, the stress threshold value of the thermal deformation monitoring area of the ceramic base is 50 MPa, and the size threshold value of the total deformation is 0.1 mm.

[0049] Optionally, the matching gap between the protective shell and the ceramic base is 30-70 μm.

[0050] Specifically, the piezoelectric sensing unit is composed of a piezoelectric ceramic layer and a polarization electrode layer formed on the surface thereof. The piezoelectric ceramic layer adopts a piezoelectric ceramic material that can work stably at high temperatures of 600℃ and above for a long time, preferably a bismuth layer structure or a perovskite structure. The polarization electrode layer adopts a high-temperature conductive material suitable for additive manufacturing to ensure the electrical stability and reliability of the electrode at high temperatures, preferably platinum, platinum alloy or nickel.

[0051] Specifically, the signal transmission line also adopts a high-temperature conductive material suitable for additive manufacturing. One end of the signal transmission line is connected to the polarization electrode of the piezoelectric sensing unit, then extends along the predetermined path, and finally forms a solder pad structure for external connection at a specified position on the outer surface of the ceramic core shell, thereby forming a continuous electrical connection path together with the protective shell and the piezoelectric sensing unit. Preferably, the signal transmission line is embedded inside the composite structure composed of the ceramic base and the protective shell, and its wiring path passes through the reinforcement rib area of the ceramic base or through the simulated low-stress area.

[0052] When the above integrated ceramic core shell deforms due to heating during the casting process, the deformation stress is transmitted to the piezoelectric sensing unit through the protective shell. The piezoelectric sensing unit converts mechanical stress into electrical signals based on the piezoelectric effect. The electrical signals are transmitted to the external data acquisition and processing system through the signal transmission line. By monitoring the shift of the piezoelectric sensing unit resonance peak, the real-time thermal deformation of the ceramic core shell at high temperature can be calculated.

[0053] According to a second aspect of the present application, a preparation method of an integrated piezoelectric sensing ceramic core shell is provided, referring to Figure 1 The preparation method comprises the following steps:

[0054] S1, determining a monitoring area of a ceramic base based on thermal-mechanical coupling simulation analysis, and constructing a three-dimensional digital model of the ceramic core shell;

[0055] S2, based on the three-dimensional digital model, printing the ceramic base using an additive manufacturing process;

[0056] S3, using an additive manufacturing process, printing a piezoelectric sensing unit and its polarization electrode in the monitoring area of the ceramic base;

[0057] S4, printing a protective shell covering the piezoelectric sensing unit and synchronously printing a signal transmission line through a multi-material additive manufacturing process;

[0058] S5, sintering the printed green body;

[0059] S6, polarizing the piezoelectric sensing unit through the signal transmission line.

[0060] The above step S1 specifically comprises:

[0061] S11, determining the monitoring area of the ceramic core shell based on thermal-mechanical coupling simulation analysis;

[0062] Specifically, based on the actual working conditions of the ceramic core shell in the target thermal processing environment, a computer aided engineering (CAE) thermal-mechanical coupling model is established. The actual working conditions include temperature field distribution, metal liquid static pressure and constraints caused by casting solidification shrinkage. Through simulation calculation, the stress distribution nephogram and the deformation nephogram of the ceramic core shell under high temperature are obtained; the area where the equivalent stress value exceeds the preset threshold value, or the area where the total deformation exceeds the preset threshold value, is determined as the monitoring area of the thermal deformation of the ceramic core shell.

[0063] In this embodiment, the preset threshold value of the equivalent stress value is 50MPa, and the preset threshold value of the total deformation is 0.1mm.

[0064] S12, constructing a three-dimensional digital model integrating multiple materials.

[0065] Specifically, the multi-solid modeling function of computer aided design (CAD) software is used to construct a three-dimensional digital model of the ceramic matrix fused piezoelectric sensing unit, its protective shell and signal transmission line in the same design environment. A mounting groove is provided in the monitoring area of the ceramic matrix, the inner cavity shape of the mounting groove is complementary to the shape of the protective shell; the piezoelectric sensing unit is located in the mounting groove and is encapsulated by the protective shell. The signal transmission line is laid in the composite structure of the ceramic matrix and the protective shell, one end of which is connected to the polarized electrode of the piezoelectric sensing unit, and the other end extends to the outer surface of the ceramic core shell.

[0066] In the mounting groove, the cavity shape is complementary to the shape of the protective shell, and the fitting gap between the ceramic matrix and the protective shell is set based on the sintering shrinkage rate of the silica-based ceramic material to compensate for the dimensional change during sintering. During the subsequent sintering process, the two materials form a firm sintering bond through densification shrinkage. The path of the signal transmission line extends along the reinforcing ribs of the ceramic matrix, or is laid in the low stress area determined by CAE simulation; at the same time, the end of the signal transmission line is provided with a pad structure for external electrical connection.

[0067] In this embodiment, the low stress area is the area where the first principal stress value is continuously lower than 50 MPa in the CAE simulation. The path of the signal transmission line maintains a distance of not less than 0.1 mm from any outer surface of the ceramic core shell and any inner surface of the cavity of the ceramic core shell. The pad structure is composed of platinum paste integrally formed with the signal transmission line, with a thickness of not less than 0.1 mm and a planar size of not less than 1 1mm 2 .

[0068] The above step S2 specifically includes:

[0069] Specifically, the three-dimensional digital model constructed in step S1 is imported into an additive manufacturing equipment that can be used for multi-material forming; a silica-based ceramic material is selected as the forming material, and the green body of the ceramic matrix is formed by layer-by-layer printing according to the model through the additive manufacturing process; when the printing is performed to the monitoring area, the mounting groove is printed according to the three-dimensional digital model. The preformed ceramic matrix with the built-in mounting groove is completed.

[0070] In this embodiment, the silica-based ceramic material is a photocurable ceramic slurry with a solid content of 75-86wt%, and the particle size of the ceramic powder is 1-20µm; a photocurable 3D printing technology is used, with a printing layer thickness of 40-80µm and a single layer exposure energy of 40-70mW.

[0071] After printing, the obtained green body is subjected to debinding treatment, heated to 500-650℃ at a heating rate of 0.5-2℃ / min in air atmosphere, and kept for 1-10 hours.

[0072] The step S3 specifically includes:

[0073] Specifically, after printing the ceramic matrix and the mounting groove, integrated printing of the piezoelectric sensing unit is performed: the mounting groove is precisely positioned and calibrated by the visual positioning system of the printing equipment; the material switching system is started to switch the printing material from the silica-based ceramic slurry to the piezoelectric ceramic slurry, and the piezoelectric ceramic slurry is continuously deposited into the mounting groove by micro-droplet jetting technology to form the piezoelectric sensing unit in situ. In this process, the ceramic matrix residual heat and the heat of the newly printed piezoelectric ceramic slurry are utilized to make both in a semi-molten state at the contact interface and diffuse with each other, thereby realizing firm interface bonding. Then, the printing material is switched to high-temperature conductive slurry to print the polarization electrode on the surface of the formed piezoelectric sensing unit.

[0074] In this embodiment, the selected piezoelectric ceramic slurry is selected from bismuth layer-structured or perovskite-structured piezoelectric ceramic materials, and the solid content of the piezoelectric ceramic slurry is 75-86wt%, and the viscosity is 1000-2000mpa·s. When printing the piezoelectric sensing unit, a micro-droplet jetting type print head is used, and the nozzle diameter is 0.1-0.8mm; the printing temperature is 80-120℃. The conductive phase of the high-temperature conductive slurry is selected from platinum, platinum alloy or nickel metal.

[0075] The step S4 specifically includes:

[0076] Specifically, after printing the piezoelectric sensing unit and the polarization electrode, the packaging and wiring printing is started. The material switching system switches back to the silica-based ceramic slurry, and the high-temperature conductive slurry printing system is started synchronously.

[0077] Through the coordinated work of multiple print heads and path planning, the high-temperature conductive slurry is printed to the preset track to form the signal transmission line while the protective shell structure is printed. The line starts from the polarization electrode, and is wrapped by the subsequently deposited ceramic slurry during the printing process, so as to be completely embedded inside the protective shell structure, and finally the end point of the line is exposed to the outer surface of the ceramic core shell. During the printing process, the deposited slurry area is subjected to local solidification by infrared irradiation to stabilize the line shape and ensure the interface quality between the heterogeneous materials.

[0078] In this embodiment, the printing material of the protective shell is consistent with the ceramic matrix, and the printing material of the signal transmission line is consistent with the polarization electrode.

[0079] The step S5 specifically includes:

[0080] Specifically, after the printing of all the structures is completed, the ceramic core shell body is subjected to an integrated sintering treatment. This process sinter the ceramic matrix and the protective shell completely and ensures the stable integration of the piezoelectric sensing unit and the signal transmission line inside. After sintering, the electrical properties and resonance properties of the integrated piezoelectric sensing unit in a high-temperature environment are verified by impedance analysis and other means to ensure that it meets the monitoring requirements.

[0081] In the present embodiment, the integrated sintering treatment is carried out in an atmosphere sintering furnace. First, the debinding and glue removal is carried out: the temperature is raised from room temperature to 500-650℃ at a rate of 0.5-2℃ / min and kept for 1-10 hours to completely remove various organic binders; then high-temperature co-sintering is carried out: the temperature is raised to a sintering temperature of 1100-1350℃ at a rate of 1-6℃ / min under an argon protective atmosphere, and kept for 2-10 hours to completely densify the silica-based ceramic matrix and the protective shell, and to achieve stable combination with the internal piezoelectric sensing unit and the lead wire.

[0082] The above step S6 specifically includes:

[0083] Specifically, after sintering, the piezoelectric sensing unit integrated inside the ceramic core shell is subjected to polarization treatment to activate its piezoelectric properties. Through the pad structure exposed on the outer surface in step S4, a high-voltage direct current electric field is applied to the built-in signal transmission line and the polarization electrode.

[0084] In the present embodiment, the polarization treatment is carried out in a silicone oil bath, the polarization temperature is 150-220℃, the applied direct current electric field strength is 1-5kV / mm, and the polarization time is 10-50min.

[0085] According to a third aspect of the present application, a monitoring method for the integrated ceramic core shell with piezoelectric sensing is proposed, as shown in Figure 2 The monitoring method includes the following steps:

[0086] Through experimental calibration, a corresponding relationship model between the resonance frequency shift of the piezoelectric sensing unit and the thermal deformation of the ceramic core shell is established;

[0087] During the hot working process, the resonance frequency data of the piezoelectric sensing unit of the ceramic core shell are collected in real time;

[0088] Based on the established corresponding relationship model, the collected resonance frequency data are converted into thermal deformation and the monitoring results are output, and when the thermal deformation exceeds a preset threshold, a warning signal is triggered.

[0089] The above step S1 specifically includes:

[0090] Specifically, the built-in piezoelectric sensing integrated ceramic core shell sample as proposed in the first aspect is calibrated in an experimental environment. The electrical signal of the built-in piezoelectric sensing unit is excited and read by a precision impedance analyzer to obtain the initial value of the resonant frequency. The real deformation of the sample during heating is measured synchronously by a thermal mechanical analyzer or other high-precision deformation measuring device. By applying different thermal loads, a plurality of corresponding data of the resonant frequency shift and the real thermal deformation are obtained. The linear fitting of the plurality of data is performed by a computer to establish a linear correspondence model between the resonant peak shift of the piezoelectric sensing unit and the thermal deformation of the ceramic core shell, thereby completing the establishment and calibration of the model. The linear correspondence model between the resonant peak shift of the piezoelectric sensing unit and the thermal deformation of the ceramic core shell is

[0091]

[0092] wherein, is the real thermal deformation, K is a calibration coefficient, ΔFr is the resonant frequency shift.

[0093] The above step S2 specifically includes:

[0094] Specifically, the built-in piezoelectric sensing integrated ceramic core shell to be monitored is placed in a high-temperature box furnace, and the piezoelectric sensing unit thereof is connected to an external precision impedance analyzer through a signal transmission line. The box furnace is controlled to operate according to a preset temperature rising-maintaining-falling process curve to simulate the actual hot processing environment. At the same time, the impedance analyzer continuously excites the piezoelectric sensing unit and dynamically records the real-time change data of the resonant frequency thereof at a set scanning frequency and measurement accuracy.

[0095] Optionally, the scanning frequency of the impedance analyzer is set to be not less than 1 time / second to ensure the capture of the dynamic process of thermal deformation.

[0096] The above step S3 specifically includes:

[0097] Specifically, the resonant frequency shift collected in real time is converted into the corresponding thermal deformation of the ceramic core shell by the calibration model pre-established and stored in step S1. Finally, the change of the thermal deformation with time or temperature is displayed and output in real time in the form of a data chart or a curve for the operator to monitor and analyze. The calculated thermal deformation is compared with the preset safety threshold in real time; when the monitored thermal deformation exceeds the safety threshold, an audible and light alarm is triggered or a warning information is sent to the control terminal to prompt the operator to adjust the process parameters in time.

[0098] The above merely describes some specific embodiments of the present application, and the protection scope of the present application is not limited thereto. Any person skilled in the art, according to the technical solution and the inventive concept of the present application, can make equivalent replacements or changes within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

[0099] It should be noted that the relative terms, such as first and second, and the like, are used herein only to distinguish one entity or action from another, and do not necessarily require or imply any actual such relationship or order between or among these entities or actions. Also, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "comprises a" does not, without more limitations, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0100] It should be noted that, in the description of the present specification, the description referring to the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. The illustrative description of the above terms in the present specification does not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. Furthermore, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction.

Claims

1. An integrated ceramic core and shell for integrating piezoelectric sensing, characterized in that, include: The ceramic matrix is ​​formed by photopolymerization 3D printing of a silica-based ceramic slurry with a solid content of 75-86 wt% and a ceramic powder particle size of 1-20 µm. At least one piezoelectric sensing unit is embedded in the monitoring area of ​​the ceramic substrate by an additive manufacturing process. The piezoelectric sensing unit includes a piezoelectric ceramic layer formed by micro-droplet jetting technology from a piezoelectric ceramic slurry with a solid content of 75-86wt% and a polarized electrode layer formed on its surface. The protective shell is formed and sealed to the piezoelectric sensing unit by additive manufacturing process. A fitting gap is formed between the protective shell and the ceramic substrate to compensate for sintering shrinkage. The value of the fitting gap is in the range of 30-70μm. The signal transmission line is formed synchronously with the protective shell through additive manufacturing process and is embedded in the protective shell. One end of the signal transmission line is connected to the polarized electrode layer, and the other end extends to the outer surface of the ceramic core shell.

2. The integrated ceramic core and shell for integrated piezoelectric sensing according to claim 1, characterized in that: The monitoring area is determined based on the thermo-mechanical coupling simulation analysis of ceramic core and shell during hot processing. The monitoring area is the region in the simulation results where the mean stress value exceeds a preset stress threshold or the total deformation exceeds a preset deformation threshold.

3. A method for fabricating an integrated ceramic core and shell for integrating piezoelectric sensing, used to fabricate an integrated ceramic core and shell for integrating piezoelectric sensing as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. Based on thermo-mechanical coupling simulation analysis, the monitoring area of ​​the ceramic matrix is ​​determined, and a three-dimensional digital model of the ceramic core and shell is constructed. S2. Based on the aforementioned three-dimensional digital model, an additive manufacturing process is used to print and form a ceramic substrate; S3. Using additive manufacturing process, the piezoelectric sensing unit and its polarization electrode are printed in the monitoring area of ​​the ceramic substrate. S4. Using multi-material additive manufacturing process, print the protective shell covering the piezoelectric sensing unit and simultaneously print the signal transmission line. S5. Sinter the printed green blank; S6. The piezoelectric sensing unit is polarized through the signal transmission line; In step S2, a silica-based ceramic slurry with a solid content of 75-86 wt% and a ceramic powder particle size of 1-20 µm is used; in step S3, a piezoelectric ceramic slurry with a solid content of 75-86 wt% is used; and in step S4, a 30-70 µm gap is formed between the protective shell and the ceramic substrate.

4. The method for preparing the integrated ceramic core and shell with integrated piezoelectric sensing according to claim 3, characterized in that: In step S1, the construction of the three-dimensional digital model of the ceramic core and shell includes constructing a three-dimensional digital model of the ceramic substrate integrating the piezoelectric sensing unit, the protective shell, and the signal transmission line; wherein, a mounting groove is generated in the monitoring area of ​​the ceramic substrate, the inner cavity shape of the mounting groove is complementary to the outer shape of the protective shell; and the layout path of the signal transmission line is planned.

5. The method for preparing an integrated ceramic core and shell with integrated piezoelectric sensing according to claim 3, characterized in that: In step S2, photopolymer 3D printing is used to print a ceramic substrate with mounting grooves by controlling the printing layer thickness and exposure energy; the layer thickness of the photopolymer 3D printing is 40-80µm, and the single-layer exposure energy is 40-70mW.

6. The method for preparing an integrated ceramic core and shell with integrated piezoelectric sensing according to claim 3, characterized in that: In step S3, the piezoelectric sensing unit is printed using microdroplet jetting technology to fill the mounting groove with piezoelectric ceramic slurry. The printing temperature is 80℃-120℃.

7. The method for preparing an integrated ceramic core and shell with integrated piezoelectric sensing according to claim 3, characterized in that: In step S5, the sintering process includes: heating to 500-650°C in an air atmosphere and holding at that temperature to complete degreasing, followed by heating to 1100-1350°C in an argon protective atmosphere and sintering and holding at that temperature.

8. The method for preparing an integrated ceramic core and shell with integrated piezoelectric sensing according to claim 3, characterized in that: In step S6, the polarization treatment includes: applying a DC electric field of 1-5 kV / mm at a temperature of 150-220°C in a polarizing liquid environment for 10-50 min.

9. A method for monitoring an integrated ceramic core and shell with integrated piezoelectric sensing, used to monitor the integrated ceramic core and shell with integrated piezoelectric sensing as described in any one of claims 1-2, characterized in that, Includes the following steps: Through experimental calibration, a model was established to establish the correspondence between the resonant frequency shift of the piezoelectric sensing unit and the thermal deformation of the ceramic core and shell. During the hot working process, the resonant frequency data of the piezoelectric sensing unit is collected in real time; Based on the established correspondence model, the collected resonant frequency data is converted into thermal deformation and the monitoring results are output. When the thermal deformation exceeds the preset threshold, an early warning is triggered.

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